class_docstr: VectorEnv where each env is run sequentially.
  
  The purpose of this VectorEnv is to help debugging. For speed, you should
  use MultiprocessVectorEnv if possible.
  
  Args:
      env_fns (list of gym.Env): List of gym.Env.
code: def close(self):
      for env in self.envs:
          env.close()
  
file_path: pfrl/pfrl/envs/serial_vector_env.py
imports: import numpy
  import pfrl
label_desc: Use image node_id 5 for calling the SerialVectorEnv obj's underlying member method code with example usage: obj.close() without return types